The time zone of each position is connected to the Location. You can add/edit the location by navigating to the Opening settings (actions > "edit opening settings")
Set Calendar to match position time zone
If you are located in a different time zone and would like the calendar availability to match the position time zone, you can do so by hovering over your name in the top right corner and select "my profile".
in "My Profile" checkmark the box "Display sessions in position time zone on the applicant table" like so:
Save and you're all set!